Series-Connected Multi-Phase Inverters for Voltage Stress Reduction
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Solution Overview
Problem
Current adjustable speed drives (ASDs) for high-power and medium-voltage applications in electric motors face inefficiencies and cost challenges, particularly in industrial settings, where energy savings are significant but not fully realized due to limitations in power electronics and motor design.
Innovation Solution
The implementation of a multi-phase inverter system with a series connection of two multi-phase inverters, each connected to different single-phase windings of an electric machine, allowing for adjustable speed control and energy efficiency improvements through a multi-level converter module that reduces voltage stresses and accommodates various voltage levels and power ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional fixed speed drives are used in high-power and medium-voltage applications, then device complexity is reduced, but energy efficiency deteriorates and cost savings are limited
Solution Approach 1:
The converter is divided into two separate multi-phase inverters (first and second inverters) that operate independently but share a common DC input. Each inverter handles a specific set of motor windings, allowing modular design and improved energy efficiency without requiring a single complex converter system.
Solution Approach 2:
The patent introduces a dual-inverter architecture that adds a dimensional aspect to the power conversion system. By using two inverters with separate AC output sets connected to different winding groups, the system achieves better energy efficiency and control capabilities compared to conventional single-inverter designs.
2Adaptability or versatility
If series connection of two multi-phase inverters is implemented, then voltage stresses are reduced and adaptability to different voltage levels is improved, but device complexity increases
Solution Approach 1:
The voltage conversion function is segmented across two independent inverters connected in series to the DC input. Each inverter handles a portion of the voltage conversion task, reducing individual voltage stresses and improving adaptability to different voltage levels while maintaining manageable complexity through modular design.
Solution Approach 2:
The series-connected dual-inverter configuration provides multi-functionality by accommodating various voltage levels and power ratings through a single standardized architecture. The system can adapt to different application requirements without requiring complete redesign, enhancing versatility.
3Reliability
If each inverter is connected to separate single-phase windings with independent neutral connectors, then reliability is improved through fault isolation, but device complexity increases
Solution Approach 1:
The motor windings are segmented into two independent sets, each connected to a separate inverter with its own neutral connector. This segmentation isolates faults within each inverter-winding pair, preventing cascading failures and improving overall system reliability while maintaining a manageable connection structure.
Solution Approach 2:
The independent neutral connectors act as intermediaries that electrically isolate the two inverter systems. This isolation allows each inverter to operate independently and provides fault containment, improving reliability without requiring complex interconnections between the two systems.
4Ease of manufacture
If series connection is used to reduce voltage stresses on components, then component costs are reduced, but manufacturing complexity increases
Solution Approach 1:
The power conversion system is segmented into two independent inverter modules, each handling reduced voltage stresses. This segmentation allows the use of lower-voltage-rated (and thus lower-cost) semiconductor components while achieving the required overall voltage handling capability through series connection, reducing component costs despite increased assembly complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances energy efficiency, reduces component costs, and enables the electric machine to operate with reduced torque production even in fault conditions, providing economic and environmental benefits by optimizing energy conversion in high-power applications.
Implementation Method 1
The first multi-phase inverter includes, but is not limited to, a first direct current (DC) positive line, a first DC negative line, and a first plurality of alternating current (AC) lines
Implementation Method 2
The first DC negative line is electrically coupled to the second DC positive line to connect the first multi-phase inverter and the second multi-phase inverter in series
Implementation Method 3
Each AC line of the first plurality of AC lines is configured to be connected to a single phase winding of an electric machine
Data Source
AI summary
A multi-level converter includes a first multi-phase inverter and a second multi-phase inverter. The first multi-phase inverter includes a first direct current (DC) positive line, a first DC negative line, and a first plurality of alternating current (AC) lines. Each AC line of the first plurality of AC lines is configured to be connected to a single phase winding of an electric machine. Each single phase winding is connected to a common neutral connector in a Y-winding configuration or between a pair of single phase windings in a Δ-winding configuration. The second multi-phase inverter includes a second DC positive line, a second DC negative line, and a second plurality of AC lines and is connected in a similar manner to the first multi-phase inverter. The first DC negative line is electrically coupled to the second DC positive line to connect the first multi-phase inverter and the second multi-phase inverter in series.